The present invention is directed to an electric door lock actuator of the type used in an automobile to lock and unlock the latching bolts in the automobile door. More particularly, the present invention is directed to a cam mechanism cooperating with projections on a driven gear to effect locking and unlocking motion and to allow for manual displacement of the lock mechanism and cam without necessitating displacement of the armature of the electric motor which drives the actuator.
In many currently used electric door lock mechanisms, an electric motor armature, gears and portions of the drive train are mechanically coupled to the locking mechanism. A typical system includes a latching bolt to secure the door to the frame of the automobile, an electric motor located on the inside of the door for locking or unlocking the bolt, a manually-displaceable handle inside of the door for unlatching the door, a manually-movable button, slide or similar device for locking and unlocking a latching bolt in the door, and on the exterior of the door, a handle for latching and unlatching the door and a key opening for the receipt of a key for unlocking or locking the latching bolts. The key receiving mechanism may be designed either manually to unlock the latching bolts or to energize a motor to unlock the latching bolts. At this point in time most key entry locks utilize the motion imparted by turning the key to unlock the latching bolts.
One of the problems identified with this type of system is that the manual effort required to turn the key to unlock the latching bolt may be significant. If the ambient temperature is low, or there is insufficient lubrication, or a key is particularly weak, in any of the above events, the force required to manually unlock the latching bolt may be such that the key is either twisted or broken in the process and entry to the car is denied.
It has been determined that one of the mechanisms acting to create the difficulty in manually unlocking the latching bolts is that when the electric motor, gears and the remainder of the electric drive train to the door lock actuator are mechanically coupled thereto, in order to manually displace the latching bolt, it is necessary to "back drive" the gear train and electric motor as the latching bolt is displaced. Hence, additional force on the key is required and additional work is necessary to accomplish the rotation of the motor armature and the displacement of the gear train of the actuator.
The term "back driven" as used herein defines the physical movement including rotation of the armature of the actuator motor, and the intermediate gearing between the armature and the door locking mechanism occasioned by turning a key to gain entry to a vehicle.
It has also been identified that under emergency conditions there may be times when it is necessary to unlock a car door from the inside and it is desirable to have little or no parasitic loading due to "back driving". Such emergency conditions include an accident or an electrical power source, such as the battery, has become disconnected, or the electric motor has otherwise been rendered inoperative. In these circumstances it is likewise beneficial not to have to manually "back drive" the motor to accomplish unlocking of the vehicle door.
Certain lost motion connecting devices have been utilized to isolate a door lock actuator unit drive from manual operation of a button or handle. For instance in U.S. Pat. No. 4,102,213, there is provided lost motion connection to permit an actuator to cycle even if the door lock lever is being held to preclude movement. This device does not act to isolate manual operation from electric operation to avoid "back driving" forces, but instead is directed as a safety feature so as not to destroy the door lock when the operator manually holds the lock in a locked position when the unlock button is energized.
U.S. Pat. No. 4,290,634 discloses a series of devices for connecting the manual locking and unlocking button in a car to the motive means. A lost motion relationship is disclosed between rack gear 63 and button link 62. Spring 64 is utilize to drive the rack gear to a neutral position such that the button may be displaced without moving the rack gear. In FIGS. 3 and 4 there is disclosed a mechanism for connecting an electric motor to a gear train, which is connected to a manual locking button, wherein the gear train is engaged upon sufficient centrifugal force being applied when the motor is operated. Additionally disclosed in FIGS. 5-8, is a lost motion device utilized without springs. Therein a rotating mechanism having a projection mates with a slot defined by a pair of movable arms such that when the projection is displaced in the correct direction and engages an appropriate arm it causes the device to slide on a shaft. When the rotation direction is in the wrong direction, the arm forming the slot is displaced without causing sliding motion on the shaft, and the rotating member may continue to rotate without effecting such displacement.
It is also known that at least one car manufacturer utilizes an electric door lock actuator which includes an electric motor which drives a rotating mechanism using a spring for latching and unlatching a door. This spring which is a direct part of the drive system is wound when the motor is energized such that when then motor is de-energized the spring unwinds causing the motor to be rotated backwards thereby allowing for manual operation of the locking mechanism without being required to "back drive" the motor. See, for instance, U.S. Pat. No. 4,573,723.